JERUSALEM — Masada, one of Israel’s biggest tourist attractions and a symbol of the country’s struggle for survival, is in danger of collapse after heavy rainfall four years ago damaged some of its supporting walls.

The 4,600 feet of wall damaged by the water must be fixed before irreversible harm is done, the head of the preservation department at the Israel Nature and National Parks Protection Authority, Zeev Margalit, said by telephone.

“What collapses today will be gone forever,” he warned. “Masada could fall tomorrow, or it could fall a year from now, or even 10 years from now. We have the tools to slow down the deterioration process and stop it now.”

The desert redoubt, overlooking the Dead Sea about 30 miles southeast of Jerusalem, was the site of the last stand by Jews rebelling against Roman rule 2,000 years ago and today is used as a swearing-in site for some Israeli combat units, who pledge “Masada shall not fall again.” The fortress in the Judean Desert was built as a palace by Herod the Great, who was king of Judea between the years 37 and 4 before the common era.

The Parks Authority, along with the Antiquities Authority, has asked the government for $17.8 million over the next five years to strengthen Masada’s supporting walls and carry out preservation work on other biblical-era tourist attractions throughout the country, Mr. Margalit said.

“Israel doesn’t have oil or diamonds. Instead, we have been blessed with cultural treasures. We have to protect them so we can pass them on to the next generations,” he added.

Masada is designated by the U.N. Educational, Scientific, and Cultural Organization as a world heritage site. Hundreds of Jews fled to the abandoned palace to escape the Roman army, which was putting down a rebellion in Judea. The Romans besieged the compound, and before their forces succeeded in conquering it, the Jews committed mass suicide.

Masada is “a symbol of the ancient kingdom of Israel, its violent destruction, and the last stand of Jewish patriots in the face of the Roman army,” in the year 73 of the common era, UNESCO said.

The camps, fortifications, and attack ramp constitute the most complete Roman siege works still surviving, UNESCO added.

Next week, Israel will hold a ceremony in honor of eight new cultural sites added to UNESCO’s world heritage list, Mr. Margalit said.